and the critical data of Z-propanol/COn mixtures have been calculated (critical data for modifier mole fraction 0.2: p c < 100 bar, Tc < l l ooc) ,8j,
An alternative phase deliverysystem based on piston pumps and a back-pressure regulator has been developed for capillary column SFC.Thechromatographyis not affected bythefast piston pump refill. A homogeneous on-line mixing of binary phases with simultaneous pressure programming is easily accessible without any additional computing. Acceptable reproducibilities
Method development requires the capability of fast change in modifier concentration or exchange of mobile phase components. Therefore, an on-line phase mixing is preferred rather than an off-line procedure.
In principle, pressure (density), temperature, and mobile phase composition gradients can influence the separanon process in CSFC cases, the usefulness of composltlon gradents in CSFC has not yet been shown However, results in packed column SFC show (< 3.5% RSD for external and < 2.0% RSD for internal standard methods) were found with mixtures of P-propanol/CO* as mobile phases using UV detection and split ratios of 1 :GO and 1 :120.
Variation and control ofthesplit areeasilydone bysimple flow rate volumetric changes.
temperature programming used only in
The CSFC system was based on commercial LC-(Gilson) and GC hardware (Carlo Erba Inst.) combined with a home-made pressure control unit (8, Rgure 1) [11,13]. The original pulse 394 Journal of High Resolution Chromatography